1. Technical Field
The present invention relates to an inkjet head.
2. Description of the Related Art
Today, one of the most actively developed functional inkjet fields is a method of directly performing the printing by using metal ink and an inkjet printer. This method can directly print a metal line, which is formed by undergoing the conventional processes, such as metal deposition, photolithography, and metal etching, without reference to a board. Metal lines and electrodes are essential in various semiconductor fields and electric and electronic fields, and thus their usage covers a wide range.
One of the problems currently generated when the metal lines are formed by using the direct printing method is difficulty of controlling the height of the metal line. The reason that lines or electrodes are made of metals is that the conductivity of the metals is high (i.e., the resistance is low). The conductivity of the metal lines is dependent on the shape of the cross-section as well as the conductivity of the metal.
The design or the line width is predetermined in the inkjet printing. Accordingly, an ink droplet having a certain volume is discharged to reproduce a certain line width. At this time, it is very difficult to adjust the line height. Of course, it is possible to adjust the aspect ratio of the metal line to a certain degree by using the physical properties of the ink or the surface condition of the board, but there remain several restrictions. It is also possible to increase the line height by repeatedly discharging the metal ink, but this is restricted because the designed line width should be maintained.
If a finer line were to be realized, it would be inevitable that the printed metal line has a lower height, thereby increasing the resistance and lowering the quality of the metal line.
FIG. 1A through FIG. 1B show how an inkjet head performs the printing according to the conventional art. The shape (i.e. width and height) of the discharged ink droplet on the board depends on the physical properties inherent in the ink and the surface condition, for example, the angle of contact, of the board. As shown in FIG. 1C, the metal line can be formed by repeatedly discharging and sintering various ink droplets.